1. Field of the Invention
This invention relates to an automatic paper feeder which includes an upper light source and particularly an automatic paper feeder for use with a scanner that is able to automatically feed paper and facilitate both reflective and transparent documents scanning functions.
2. Description of the Prior Art
Conventional flatbed type scanning and copying equipment such as optical scanners and copiers usually have a document placed on a transparent platform stationary, then having a scanning means moving across the transparent platform to perform scanning process. This type of scanning equipment can process only one piece of document at a time. Its operation is labor intensive and not efficient for high volume scanning work. To remedy this problem, an automatic paper feeder has been introduced. FIG. 1 shows an example of such device for scanning or copying machine use. The automatic paper feeder 1 includes a paper tray 11 which can hold a plurality of scanning documents 13 and a transmission unit 12 which has a plurality of rollers for automatically picking a sheet of document 13 at a time to feed into a channel 14. There is a cable 15 to wire the paper feeder 1 to a control circuit board 21 in a scanner 2. Then a software is employed to coordinate and control the operations of the paper feeder 1 and the scanner 2.
When in use, the transmission unit 12 picks up a document 13 and feeds it into the channel 14 until it laid upon a scanning platform 22. Then a scanning means 23 is activated to move across the scanning platform 22 to perform scanning process. After scanning completed, the transmission unit 12 discharges the document 13 from the scanning platform 22, and picks up another document in the paper tray 11 for another cycle of scanning operation.
In this type of scanner, the scanning document is laid stationary on the scanning platform during scanning process. Document movement is intermittent and becomes a drag on operation which is still not very efficient if a lot of documents are to be scanned. In addition, it suits only reflection type scanning work. As it has only a lower light source 231 located in the scanning means 23 to project light through the transparent scanning platform 22 upon the document 13 held in the channel 14. It generally is no good for transparency scanning (such as projection transparency, slide, negative film, and etc.) as the channel 14 has an allowance which makes the document cannot be held upon the platform closely or evenly. Therefore it often results in poor scanning quality such as double image, overlapping image or blurring image when performing transparency scanning.